HackerRank Alien Username Solution

Hello Programmers, In this post, you will learn how to solve HackerRank Alien Username Solution. This problem is a part of the Regex HackerRank Series.

One more thing to add, don’t straight away look for the solutions, first try to solve the problems by yourself. If you find any difficulty after trying several times, then look for the solutions. We are going to solve the  Regex HackerRank Solutions using  CPP, JAVA, PYTHON, JavaScript & PHP Programming Languages.

You can practice and submit all HackerRank problem solutions in one place. Find a solution for other domains and Sub-domain. I.e. Hacker Rank solution for HackerRank C ProgrammingHackerRank C++ ProgrammingHackerRank Java Programming, HackerRank Python ProgrammingHackerRank Linux ShellHackerRank SQL Programming, and HackerRank 10 days of Javascript.

HackerRank Alien Username Solution
HackerRank Alien Username Solution

As you already know that this site does not contain only the Hacker Rank solutions here, you can also find the solution for other problems. I.e. Web Technology, Data StructuresRDBMS ProgramsJava Programs Solutions,  Fiverr Skills Test answersGoogle Course AnswersLinkedin Assessment, and Coursera Quiz Answers.

HackerRank Alien Username Word Solution


In a galaxy far, far away, on a planet different from ours, each computer username uses the following format:

  1. It must begin with either an underscore, _ (ASCII value 95), or a period, . (ASCII value 46).
  2. The first character must be immediately followed by one or more digits in the range 0 through 9.
  3. After some number of digits, there must be 0 or more English letters (uppercase and/or lowercase).
  4. It may be terminated with an optional _ (ASCII value 95). Note that if it’s not terminated with an underscore, then there should be no characters after the sequence of 0 or more English letters.

Given n strings, determine which ones are valid alien usernames. If a string is a valid alien username, print VALID on a new line; otherwise, print INVALID.

Input Format

The first line contains a single integern, denoting the number of usernames.
Each line i of the n subsequent lines contains a string denoting an alien username to validate.


  • 1 <= n <= 100

Output Format

Iterate through each of the n strings in order and determine whether or not each string is a valid alien username. If a username is a valid alien username, print VALID on a new line; otherwise, print INVALID.

Sample Input


Sample Output



We validate the following three usernames:

  1. _0898989811abced_ is valid as it satisfies the requirements specified above. Thus, we print VALID.
  2. _abce is invalid as the beginning _ is not followed by one or more digits. Thus, we print INVALID.
  3. _09090909abcD0 is invalid as the sequence of English alphabetic letters is immediately followed by a number. Thus, we print INVALID.

HackerRank Alien Username Solution in Cpp

#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
#include <ctype.h>
using namespace std;

int foo(char *c)
    int i;
        return 0;
        return 0;
    if(c[i]=='\0')return 1;
    else if(c[i]=='_'&&c[i+1]=='\0')return 1;
    else return 0;

int main() {
    int n;
    char c[1000];
    for(int i=0;i<n;i++)
    return 0;

HackerRank Alien Username Solution in Java

import java.util.Scanner;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class Solution {

	public static void main(String[] args) {
		Pattern p=Pattern.compile("(^\\.|_)(\\d+)([a-z]|[A-Z])*(_){0,1}");
		Scanner in = new Scanner(System.in);

		int count = 0;
		int iterator = in.nextInt();
		for (int i = 0; i < iterator; i++) {
			String data = in.nextLine();
			Matcher m=p.matcher(data);

HackerRank Alien Username Solution in Python

import re
for i in range(0,n):

for l in lines:

HackerRank Alien Username Solution in JavaScript

process.stdin.on("data", function (input) {
	input = input.split('\n');
	var n = parseInt(input[0]),
		strs = input.slice(1,n+1);
	for (i=0, j=strs.length; i<j; i+=1) {
		if (strs[i].match(/^[_\.]\d+[a-z]*_?$/ig)) {
		} else {

HackerRank Alien Username Solution in PHP

$_fp = fopen("php://stdin", "r");
/* Enter your code here. Read input from STDIN. Print output to STDOUT */
fscanf($_fp, "%d", $m);
$lines = array();
for ($i = 0; $i < $m; $i++) {
    $line = trim(fgets($_fp));
    print (preg_match('/^[_\.][0-9]+[a-z]*_?$/i', $line) ? 'VALID' : 'INVALID') . PHP_EOL;

Disclaimer: This problem (Alien Username) is generated by HackerRank but the solution is provided by Chase2learn. This tutorial is only for Educational and Learning purposes.


1. How do you solve the first question in HackerRank?

If you want to solve the first question of Hackerrank then you have to decide which programing language you want to practice i.e C programming, Cpp Programing, or Java programming then you have to start with the first program HELLO WORLD.

2. How do I find my HackerRank ID?

You will receive an email from HackerRank to confirm your access to the ID. Once you have confirmed your email, the entry will show up as verified on the settings page. You will also have an option to “Make primary”. Click on that option. Read more

3. Does HackerRank detect cheating?

yes, HackerRank uses a powerful tool to detect plagiarism in the candidates’ submitted code. The Test report of a candidate highlights any plagiarized portions in the submitted code and helps evaluators to verify the integrity of answers provided in the Test.

4. Does HackerRank use camera?

No for coding practice Hackerrank does not use camera but for companies’ interviews code submission time Hackerrank uses the camera.

5. Should I put HackerRank certificate on resume?

These certificates are useless, and you should not put them on your resume. The experience you gained from getting them is not useless. Use it to build a portfolio, and link to it on your resume. 

6. Can I retake HackerRank test?

The company which sent you the HackerRank Test invite owns your Test submissions and results. It’s their discretion to permit a reattempt for a particular Test. If you wish to retake the test, we recommend that you contact the concerned recruiter who invited you to the Test and request a re-invite. 

7. What is HackerRank?

HackerRank is a tech company that focuses on competitive programming challenges for both consumers and businesses. Developers compete by writing programs according to provided specifications. Wikipedia

Finally, we are now, in the end, I just want to conclude some important message for you

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